On Feb 21, 2008, at 17.49, Kris Kennaway wrote:
benjamin thielsen wrote:
hi folks-
we've been experiencing some interesting behavior on single quad
core computers as compared to dual quad core computers.
Yes, this can happen when you run into concurrency bottlenecks in
the application or in the kernel.
it appears that adding a second processor to the system (leaving it
otherwise untouched) actually decreases performance. we've got a
small rudimentary test process, built in house, that does
postgresql queries (selects) via http requests (apache2/php5).
7.0 will perform much better than 6.x on SMP workloads in general,
however TCP I/O is not yet at the point where it can make efficient
use of many processors (there has been a lot of work on TCP in 7.0,
but it is not yet at the stage where a performance payoff will be
seen with more than about 4 CPUs). This is one of the projects that
we will be working on this year, so you can expect future releases
to have improved concurrent TCP performance.
There may be other issues, so if you like you can enable
LOCK_PROFILING and obtain a trace when your workload is running (see
the manpage). You should also try the ULE scheduler on 7.0.
i apologize - i neglected to mention that we are using ule on 7.0.
what do you guys generally endorse/recommend for local(non-network)
load/performance testing?
-ben
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